Question

Sum of n terms of arithmetic progression is 2n^2 + n then eighth term is

Answer 1

let n =1

2(1)(1)+(1)

2+1

3=S1=a1

let n=2

2(2)(2)+(2)

8+2

10=s2

s2-s1=a2

=10-3

7

a=3

d=7-3

4=d

A8=a+7d

=3+7(4)

=28+3

=31